LAUNDRY WASHING MACHINE AND METHOD FOR OPERATING THE LAUNDRY WASHING MACHINE

The present invention concerns the field of laundry washing techniques.

Specifically, the invention relates to a laundry washing machine with recirculation circuits.

The invention relates also a method for controlling said recirculation circuits.

BACKGROUND ART

Nowadays the use of laundry washing machines, both “simple” laundry washing machines (i.e. laundry washing machines which can only wash and rinse laundry) and laundry washing-drying machines (i.e. laundry washing machines which can also dry laundry), is widespread.

In the present description, therefore, the term “laundry washing machine” will refer to both a simple laundry washing machine and a laundry washing-drying machine.

Laundry washing machines generally comprise an external casing, or cabinet, provided with a washing tub which contains a rotatable perforated washing drum where the laundry is placed. A loading/unloading door ensures access to the washing drum.

Laundry washing machines typically comprise a water supply unit and a treating agents dispenser, preferably equipped with a drawer, for the introduction of water and washing/rinsing products (i.e. detergent, softener, rinse conditioner, etc.) into the washing tub.

Known laundry washing machines are typically provided with a water outlet circuit suitable for withdrawing liquid, for example dirty water, from the bottom of the washing tub to the outside. The water outlet circuit is typically provided with a controllable draining pump.

Known laundry washing machines are also typically provided with recirculation circuits.

A first known recirculation circuit which equips laundry washing machines is adapted to drain liquid from the bottom region of the washing tub and to re-admit such a liquid into an upper region of the washing tub. The first recirculation circuit is preferably provided with a terminal nozzle opportunely arranged so that the recirculated liquid is conveyed over the laundry and distribution of the same liquid over the laundry is enhanced. The first recirculation circuit is typically provided with a first controllable recirculation pump.

A second known recirculation circuit which equips laundry washing machines, or mixing circuit, is adapted to drain liquid from a bottom region of the washing tub and to re-admit such a liquid (recirculated mixing liquid) into a region of the washing tub which corresponds substantially to the same bottom region of the washing tub.

The mixing circuit is preferably realized for transferring a portion of a liquid from a bottom region of the washing tub to the same bottom region for the mixing and/or the dissolution of the products, in particular for liquid and/or powder detergent. The second recirculation circuit is typically provided with a second controllable recirculation pump.

During the washing cycle, the controlled pumps are opportunely activated at proper times to drain and/or recirculate liquid from the bottom of the washing tub.

In particular, the first and second recirculation pumps of the first and second recirculation circuits are selectively activated to recirculate liquid when necessary.

In known laundry washing machines of different type, the first and the second recirculation circuits are realized so that they comprise a first common part, namely a draining tube connected to the bottom of the washing tub, a unique controlled recirculation pump and two recirculation tubes that respectively connect the pump outlet to the upper region of the washing tub and the bottom region of the washing tub.

Between the pump outlet and the recirculation tubes a controllable valve is arranged, preferably a two-way valve, that allows the liquid to flow selectively into the first or the second recirculation tube when the recirculation pump is activated.

However, laundry washing machines of the known art pose some drawbacks.

A drawback of the laundry washing machines of the known art is the complex structural construction. According to known art, in fact, two pumps and/or one or more valves are required.

This increases the manufacturing and/or maintenance time and costs of the laundry washing machine.

A further drawback posed by this known technique is constituted by the high failure rate due to the complex structural construction.

The object of the present invention is therefore to overcome the drawbacks posed by the known technique.

It is an object of the invention to implement a laundry washing machine which has a simplified structural construction with respect to the known laundry washing machines.

It is a further object of the invention to implement a laundry washing machine that makes it possible to reduce manufacturing and/or maintenance time and costs.

It is a further object of the invention to implement a laundry washing machine that makes it possible to increase reliability thereof.

DISCLOSURE OF INVENTION

Applicant has found that by providing a laundry washing machine comprising a washing tub external to a washing drum and a recirculation system comprising a first duct terminating at a first region of the washing tub and a second duct terminating at a second region of the washing tub and by providing a recirculation pump for conveying liquid to a bifurcation for the ducts and by providing the recirculation pump with two functioning conditions, it is possible to reach the mentioned objects.

In a first aspect thereof the present invention relates, therefore, to a laundry washing machine comprising:

- a washing tub external to a washing drum suited to receive the laundry to be washed;
- a water supply system suitable to convey water to said washing tub;
- a recirculation system for draining liquid from the bottom of said washing tub and to re-admit such liquid into a first region and a second region of said washing tub, said recirculation system comprising:
- a first duct terminating at said first region wherein said liquid may circulate to reach said washing tub;
- a second duct terminating at said second region wherein said liquid may circulate to reach said washing tub;

wherein said recirculation system comprises a recirculation pump having an inlet connected to said bottom of said washing tub and an outlet for conveying liquid to a bifurcation for said first duct and said second duct, wherein said ducts are configured so that a liquid in said first duct requires a pressure to reach said washing tub which is lower than the pressure required for a liquid in said second duct to reach said washing tub, and wherein said recirculation pump has a first functioning condition wherein liquid circulates only in said first duct to reach said washing tub and a second functioning condition wherein liquid circulates both in said first and second ducts to reach said washing tub.

With the term bifurcation it has to be meant a system that connects an inlet duct to a first outlet duct and a second outlet duct and that allows a liquid to be conveyed from the inlet duct concurrently to the first outlet duct and second outlet duct.

Preferably, the liquid continuously flows from the inlet duct concurrently to the first outlet duct and the second outlet duct.

Preferably, the bifurcation is free of any closure member, such as valve. More preferably, the first outlet duct and the second outlet duct are free of any closure member, such as valve.

According to a preferred embodiment of the invention, at said second functioning condition the recirculation pump is driven at a higher power than in the first functioning condition.

In a preferred embodiment of the invention, the recirculation pump is a variable-speed pump, wherein in the first functioning condition the recirculation pump is driven at a first speed and in the second functioning condition the recirculation pump is driven at a second speed, the second speed being higher than the first speed.

In a preferred embodiment of the invention, the recirculation pump is a variable-speed pump, wherein in the first functioning condition the recirculation pump is driven at a first speed below a threshold value and in the second functioning condition the recirculation pump is driven at a second speed above the threshold value.

According to a preferred embodiment of the invention, the recirculation pump is driven so that its speed has a pulsed waveform.

Preferably, in the first functioning condition the recirculation pump is driven so that its speed has a first pulsed waveform having a first duty cycle and in the second functioning condition the recirculation pump is driven so that its speed has a second pulsed waveform having a second duty cycle, the second duty cycle being higher than the first duty cycle.

As known, the duty cycle is the fraction of one period in which a system is active. In the present invention, the duty cycle is the fraction of one period in which the recirculation pump is switched on.

Preferably, in the first functioning condition the recirculation pump is driven so that its speed has a first pulsed waveform having a first duty cycle below a threshold value and in the second functioning condition the recirculation pump is driven so that its speed has a second pulsed waveform having a second duty cycle above the threshold value.

In a preferred embodiment of the invention, the recirculation pump is a variable-speed pump, wherein in the first functioning condition the recirculation pump is driven so that its speed has a first pulsed waveform having a first average speed and in the second functioning condition the recirculation pump is driven so that its speed has a second pulsed waveform having a second average speed, the second average speed being higher than the first average speed.

In a preferred embodiment of the invention, the recirculation pump is a variable-speed pump, wherein in the first functioning condition the recirculation pump is driven so that its speed has a first pulsed waveform having a first average speed below a threshold value and in the second functioning condition the recirculation pump is driven so that its speed has a second pulsed waveform having a second average speed above the threshold value.

With the term “average speed” it has to be meant the average speed of the recirculation pump in a predetermined time period within which the speed of the recirculation pump comprises a plurality of pulses.

According to a preferred embodiment of the invention, the machine comprises an outlet duct connected to the recirculation pump outlet and the bifurcation is realized in the outlet duct.

According to a further preferred embodiment of the invention, the recirculation pump outlet is realized at a body portion of the recirculation pump and the bifurcation is realized at the body portion of the recirculation pump.

In a preferred embodiment of the invention, the machine further comprises a treatment agents dispenser to supply one or more treating agents into the washing tub.

Preferably, the first region is a bottom part of the washing tub and/or the second region is an upper part of the washing tub.

According to a preferred embodiment of the invention, the first duct defines a first volume and the second duct defines a second volume, wherein the first volume is lower than the second volume.

According to a preferred embodiment of the invention, the ducts have the same diameter, wherein the first duct has a lower length than the second duct.

In a further aspect, the present invention relates to a method for operating a laundry washing machine comprising:

- a washing tub external to a washing drum suited to receive the laundry to be washed;
- a water supply system suitable to convey water to said washing tub;
- a recirculation system for draining liquid from the bottom of said washing tub and to re-admit such liquid into a first region and a second region of said washing tub, said recirculation system comprising:
- a first duct terminating at said first region wherein said liquid may circulate to reach said washing tub;
- a second duct terminating at said second region wherein said liquid may circulate to reach said washing tub;
- a recirculation pump having an inlet connected to said bottom of said washing tub and an outlet for conveying liquid to a bifurcation for said first duct and said second duct;

wherein said ducts are configured so that a liquid in said first duct requires a pressure to reach said washing tub which is lower than the pressure required for a liquid in said second duct to reach said washing tub; wherein said recirculation pump is driven at a first functioning condition to circulate liquid only in said first duct to reach said washing tub and is driven at a second functioning condition to circulate liquid both in said first and second ducts to reach said washing tub.

According to a preferred embodiment of the invention, at said second functioning condition the recirculation pump is driven at a higher power than in the first functioning condition.

In a preferred embodiment of the invention, the recirculation pump is a variable-speed pump, wherein in the first functioning condition the recirculation pump is driven at a first speed below a threshold value and in the second functioning condition the recirculation pump is driven at a second speed above the threshold value.

According to a preferred embodiment of the invention, the recirculation pump is driven so that its speed has a pulsed waveform.

Preferably, in the first functioning condition the recirculation pump is driven so that its speed has a first pulsed waveform having a first duty cycle and in the second functioning condition the recirculation pump has a second pulsed waveform having a second duty cycle, the second duty cycle being higher than the first duty cycle.

In a preferred embodiment of the invention, the recirculation pump is a variable-speed pump, wherein in the first functioning condition the recirculation pump is driven so that its speed has a first pulsed waveform having a first average speed below a threshold value and in the second functioning condition the recirculation pump is driven so that its speed has a second pulsed waveform having a second average speed above the threshold value.

Preferably, the first region is a bottom part of the washing tub and/or the second region is an upper part of the washing tub.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention will be highlighted in greater detail in the following detailed description of some of its preferred embodiments, provided with reference to the enclosed drawings. In the drawings, corresponding characteristics and/or components are identified by the same reference numbers. In particular:

FIG. 1 shows a perspective view of a laundry washing machine according to a first embodiment of the invention;

FIG. 2 shows the laundry washing machine of FIG. 1 with same external casing sides removed therefrom;

FIG. 3 shows a schematic view of the laundry washing machine of FIG. 2;

FIG. 4 shows some elements of the laundry washing machine of FIG. 2 isolated from the rest;

FIG. 5 shows some elements of FIG. 4 isolated from the rest;

FIG. 6 shows elements of FIG. 5 from another point of view;

FIG. 7 shows some elements of FIG. 5 isolated from the rest;

FIG. 8 shows a partial sectional view of FIG. 7;

FIG. 9A shows a schematic view of the laundry washing machine with the recirculation pump in a first functioning condition;

FIG. 9B shows a schematic view of the laundry washing machine with the recirculation pump in a second functioning condition;

FIG. 10A shows the circulation pump speed as a function of the time in the first functioning condition according to a first preferred embodiment of the method of the invention;

FIG. 10B shows the circulation pump speed as a function of the time in the second functioning condition according to a first preferred embodiment of the method of the invention;

FIG. 11A shows the circulation pump speed as a function of the time in the first functioning condition according to a second preferred embodiment of the method of the invention;

FIG. 11B shows the circulation pump speed as a function of the time in the second functioning condition according to a second preferred embodiment of the method of the invention;

FIG. 12A shows the circulation pump speed as a function of the time in the first functioning condition according to a third preferred embodiment of the method of the invention;

FIG. 12B shows the circulation pump speed as a function of the time in the second functioning condition according to a third preferred embodiment of the method of the invention;

FIG. 13 shows a further embodiment of FIG. 5;

FIG. 14 shows a detail of FIG. 13;

FIG. 15 shows a further embodiment of FIG. 5;

FIG. 16 shows an element of FIG. 15 isolated from the rest;

FIG. 17 is a plan view from above of the element of FIG. 16;

FIG. 18 is a plan sectional view taken along line XVII°-XVII° of FIG. 17;

FIG. 19 shows a further embodiment of FIG. 5;

FIG. 20 shows an element of FIG. 19 isolated from the rest;

FIG. 21 is a plan frontal view of the element of FIG. 20;

FIG. 22 is a plan sectional view taken along line XXI°-XXI° of FIG. 21.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention has proved to be particularly advantageous when applied to laundry washing machines, as described below. It should in any case be underlined that the present invention is not limited to laundry washing machines. On the contrary, the present invention can be conveniently applied to laundry washing-drying machines (i.e. laundry washing machines which can also dry laundry).

With reference to FIGS. 1 to 3, a preferred embodiment of a laundry washing machine 1 according to the invention is described, in which also a method according to a preferred embodiment of the invention is implemented.

The laundry washing machine 1 preferably comprises an external casing or cabinet 2, a washing tub 3, a container 4, preferably a perforated washing drum 4, where the laundry to be treated can be loaded.

The washing tub 3 and the washing drum 4 both preferably have a substantially cylindrical shape.

The washing tub 3 is preferably connected to the cabinet 2 by means of an elastic bellows 7, or gasket. The bellows 7 is preferably S-shaped.

The cabinet 2 is provided with a loading/unloading door 8 which allows access to the washing drum 4.

The washing drum 4 is advantageously rotated by an electric motor, not illustrated, which preferably transmits the rotating motion to the shaft of the washing drum 4, advantageously by means of a belt/pulley system. In a different embodiment of the invention, the motor can be directly associated with the shaft of the drum 4.

The washing drum is advantageously provided with holes which allow the liquid flowing therethrough. Said holes are typically and preferably homogeneously distributed on the cylindrical side wall of the drum 4.

The bottom region 3a of the washing tub 3 preferably comprises a seat 15, or sump, suitable for receiving a heating device 10. The heating device 10, when activated, heats the liquid inside the sump 15.

In different embodiments, nevertheless, the bottom region of the washing tub may be configured differently. For example, the bottom region of the washing tub may not comprise a seat for the heating device. The heating device may be advantageously placed in the annular gap between the washing tub and the washing drum.

Preferably, laundry washing machine 1 comprises a device 19 suited to sense (or detect) the liquid level inside the washing tub 3.

The sensor device 19 preferably comprises a pressure sensor which senses the pressure in the washing tub 3. From the values sensed by the sensor device 19 it is possible to determine the liquid level of the liquid inside the washing tub 3. In another embodiment, not illustrated, laundry washing machine may preferably comprise (in addition to or as a replacement of the pressure sensor) a level sensor (for example mechanical, electro-mechanical, optical, etc.) adapted to sense (or detect) the liquid level inside the washing tub 3.

A water supply circuit 5 is preferably arranged in the upper part of the laundry washing machine 1 and is suited to supply water into the washing tub 3 from an external water supply line E. The water supply circuit 5 preferably comprises a controlled supply valve 5a which is properly controlled, opened and closed, during the washing cycle. The water supply circuit of a laundry washing machine is well known in the art, and therefore it will not be described in detail.

The laundry washing machine 1 advantageously comprises a treating agents dispenser 14 to supply one or more treating agents into the washing tub 3 during a washing cycle. Treating agents may comprise, for example, detergents, rinse additives, fabric softeners or fabric conditioners, waterproofing agents, fabric enhancers, rinse sanitization additives, chlorine-based additives, etc.

Preferably, the treating agents dispenser 14 comprises a removable drawer 6 provided with various compartments suited to be filled with treating agents.

In a preferred embodiment, not illustrated, the treating agents dispenser may comprise a pump suitable to convey one or more of said agents from the dispenser to the washing tub.

In the preferred embodiment here illustrated, the water is supplied into the washing tub 3 from the water supply circuit 5 by making it flow through the treating agents dispenser 14 and then through a supply pipe 18.

In an alternative embodiment of the invention, a further separate water supply pipe can be provided, which supplies exclusively clean water into the washing tub from the external water supply line.

In further preferred embodiments, not illustrated herein, a water softening device may preferably be arranged/interposed between the external water supply line and the treating agents dispenser so as to be crossed by the fresh water flowing from the external water supply line. The water softening device, as known, is structured for reducing the hardness degree of the fresh water drawn from the external water supply line E and conveyed to the treating agents dispenser.

In a different embodiment, the water softening device may be arranged/interposed between the external water supply line and the washing tub, so as to be crossed by the fresh water flowing from the external water supply line and conveying it directly to the washing tub.

Laundry washing machine 1 preferably comprises a water outlet circuit 25 suitable for withdrawing liquid from the bottom region 3a of the washing tub 3.

The water outlet circuit 25 preferably comprises a main pipe 17, a draining pump 27 and an outlet pipe 28 ending outside the cabinet 2.

The water outlet circuit 25 preferably further comprises a filtering device 12 arranged between the main pipe 17 and the draining pump 27. The filtering device 12 is adapted to retain all the undesirable bodies (for example buttons that have come off the laundry, coins erroneously introduced into the laundry washing machine, etc.). The filtering device 12 can preferably be removed, and then cleaned, through a gate 13 placed advantageously on the front wall of the cabinet 2 of the laundry washing machine 1, as illustrated in FIG. 1.

The main pipe 17 connects the bottom region 3a of the washing tub 3 to the filtering device 12.

In a further embodiment, not illustrated, the filtering device 12 may be provided directly in the washing tub 3, preferably obtained in a single piece construction with the latter. In this case, the filtering device 12 is fluidly connected to the outlet of the washing tub 3, in such a way that water and washing liquid drained from the washing tub 3 enters the filtering device 12.

Activation of the draining pump 27 drains the liquid, i.e. dirty water or water mixed with washing and/or rinsing products, from the washing tub 3 to the outside.

According to the invention, the laundry washing machine 1 then preferably comprises a recirculation system 20, as better illustrated in FIG. 4, which is adapted to drain liquid from the bottom region 3a of the washing tub 3 and to re-admit such a liquid into a first region 3a and a second region 3b of the washing tub 3, as better described below.

Preferably, the first region 3a of the washing tub 3 substantially corresponds to the same bottom region 3a of the washing tub 3. The liquid is preferably re-admitted to the bottom region 3a of the washing tub 3 for the mixing and/or the dissolution of the products, in particular of the detergent. Mixing and/or dissolution of a product is preferably carried out during a washing cycle when one of the products is supplied into the washing tub 3 from the treating agents dispenser 14.

Preferably, the second region 3b of the washing tub 3 substantially corresponds to an upper region 3b of the washing tub 3. The liquid is preferably re-admitted to the upper region 3b of the washing tub 3 in order to improve wetting of the laundry inside the washing drum 4. This action is preferably carried out at the beginning of a washing cycle when the laundry needs to be completely soaked. Furthermore, this action is preferably carried out during rinsing phases at the beginning of the washing cycle or during rinsing phases in successive steps of the washing cycle.

The recirculation system 20 preferably comprises a first recirculation line 30 for conveying liquid to the first region 3a of the washing tub 3 and a second recirculation line 40 for conveying liquid to the second region 3b of the washing tub 3.

The first recirculation line 30 preferably comprises a first duct 33 terminating at said first region 3a, preferably ending inside the sump 15. The first duct 33 is preferably provided with a terminal nozzle 33a.

The second recirculation line 40 preferably comprises a second duct 43 terminating at said second region 3b, preferably ending at the bellows 7, as better illustrated in FIG. 4. The second duct 43 is preferably provided with a terminal nozzle 43a.

The recirculation system 20 then preferably comprises a common recirculation pump 22 comprising an inlet 24 connected to the bottom 3a of the washing tub 3 and an outlet 26 for conveying liquid to the first and second recirculation lines 30, 40, more preferably to the first and second ducts 33, 43.

Inlet 24 of the recirculation pump 22 is preferably connected to the bottom 3a of the washing tub 3 through a pipe 32 preferably connected to the filtering device 12.

According to an aspect of the invention, outlet 26 of the recirculation pump 22 conveys liquid to the first duct 33 and the second duct 43 through a bifurcation 60.

Preferably, an outlet duct 62 is connected to the pump outlet 26 and the bifurcation 60 is realized at an outlet duct end 62a thereof. The bifurcation 60 is preferably Y shaped.

Preferably, the liquid continuously flows from the inlet duct concurrently to the first outlet duct and the second outlet duct.

Preferably, the bifurcation is free of any closure member, such as valve. More preferably, the first outlet duct and the second outlet duct are free of any closure member, such as valve.

According to an advantageous aspect of the invention, the recirculation pump 22 is driven at a first functioning condition to circulate liquid only in the first recirculation line 30 to reach the washing tub 3, as schematically illustrated in FIG. 9A, and the recirculation pump 22 is driven at a second functioning condition to circulate liquid both in the first recirculation line 30 and the second recirculation line 40 to reach the washing tub 3, as schematically illustrated in FIG. 9B.

More preferably, the recirculation pump 22 is driven at a first functioning condition to circulate liquid only in the first duct 33 to reach the washing tub 3 and the recirculation pump 22 is driven at a second functioning condition to circulate liquid both in the first duct 33 and the second duct 43 to reach the washing tub 3.

It should be noted that when the recirculation pump 22 is driven at the first functioning condition, the liquid may partially fill the second recirculation line 40, in particular the second duct 43, but it does not reach the washing tub 3, as schematically illustrated in FIG. 9A.

Furthermore, it should be noted that when the liquid circulates in the first duct 33, either when the recirculation pump 22 is driven at the first functioning condition or is driven at the second functioning condition, the liquid is preferably sprayed inside the washing tub 3 through the terminal nozzle 33a, more preferably sprayed inside the sump 15.

In a first operational condition, the liquid may be sprayed inside the washing tub 3, more preferably inside the sump 15, while the liquid level inside the washing tub 3 is lower than the position of the terminal nozzle 33a, as schematically illustrated in FIGS. 9A and 9B where the liquid level inside the washing tub 3, in particular inside the sump 15, is at a first level L1.

In a different operational condition, the liquid may also be conveyed inside the washing tub 3, more preferably inside the sump 15, while the liquid level inside the washing tub 3 is equal or higher than the position of the terminal nozzle 33a, as schematically illustrated in FIGS. 9A and 9B where the liquid level inside the washing tub 3, in particular inside the sump 15, is at a second level L2 (indicated with a dashed line).

Preferably, with the term “functioning condition” it is meant the driving power of the pump.

Therefore, according to an advantageous aspect of the invention, the recirculation pump 22 is preferably driven at a first power to circulate liquid only in the first recirculation line 30 to reach the washing tub 3 and the recirculation pump 22 is preferably driven at a second power to circulate liquid both in the first recirculation line 30 and the second recirculation line 40 to reach the washing tub 3, wherein the second driving power is higher than the first driving power.

More preferably, the recirculation pump 22 is preferably driven at a first power to circulate liquid only in the first duct 33 to reach the washing tub 3 and the recirculation pump 22 is preferably driven at a second power to circulate liquid both in the first duct 33 and the second duct 43 to reach the washing tub 3, wherein the second driving power is higher than the first driving power.

Advantageously, during the washing cycle when the liquid needs to be re-admitted to the bottom region 3a of the washing tub 3, for example for the mixing and/or the dissolution of the products, the recirculation pump 22 is driven at a first power. When the liquid needs to be re-admitted to the upper region 3b of the washing tub 3, preferably to soak the laundry, the recirculation pump 22 is driven at a second power higher than the first power. In the latest, liquid is also re-admitted to the bottom region 3a of the washing tub 3 through the first recirculation line, as illustrated in FIG. 9B. Nevertheless, re-admission of the liquid to the bottom region 3a of the washing tub 3 is accepted since it does not negatively affect the soaking process.

According to an aspect of the invention, with the recirculation pump 22 in the first functioning condition the liquid may circulate only in the first recirculation line 30 and not in the second recirculation line 40 thank to the asymmetry of the two lines 30, 40.

Preferably, at this purpose, the recirculation lines 30, 40 are configured so that the liquid in the first recirculation line 30 requires a pressure P1 to reach the first region 3a of washing tub 3 which is lower than the pressure P2 required for the liquid in the second recirculation line 40 to reach the second region 3b of the washing tub 3. Symmetry of the two lines 30, 40 must therefore be avoided. More preferably, the ducts 33, 43 are configured so that the liquid in the first duct 33 requires a pressure P1 to reach the first region 3a of the washing tub 3 which is lower than the pressure P2 required for a liquid in the second duct 43 to reach the second region 3b of the washing tub 3. Symmetry of the two ducts 33, 43 must therefore be avoided.

It should be noted that the pressure required for the liquid in the first duct 33 to reach the first region 3a of the washing tub 3 may vary according to the operational condition of the same first recirculation line 30.

Namely, the pressure required for the liquid in the first duct 33 to reach the first region 3a of the washing tub 3 while the liquid level L1 inside the washing tub 3 is lower than the position of the terminal nozzle 33a, has a first value P1 which is lower than the value P1′ of the pressure required for the liquid in the first duct 33 to reach the first region 3a of the washing tub 3 while the liquid level L2 inside the washing tub 3 is equal or higher than the position of the terminal nozzle 33a.

At the same time, the value P2 of the pressure required for the liquid in the second duct 43 to reach the second region 3b of the washing tub 3 does not vary according to the operational condition of the first recirculation line 30.

Said pressure value P2 has the same value irrespective of the liquid level, L1 or L2, inside the washing tub 3.

In any case, and according to the invention, said pressure values P1, Pr for the liquid in the first duct 33 are lower than the pressure value P2 for the liquid in the second duct 43.

According to the preferred embodiment illustrated herein, the first duct 33 preferably defines a first volume V1. The first volume V1 is closely related to the size of the first duct 33 and preferably depends on diameter and length of the same. Analogously, the second duct 43 preferably defines a second volume V2. The second volume V2 is closely related to the size of the second duct 43 and preferably depends on diameter and length of the same.

According to the spatial arrangement of the components of the recirculation system 20, in particular the position of the recirculation pump 22 and the layout of the ducts 33, 43, the first volume V1 defined by the first duct 33 is lower than the second volume V2 defined by the second duct 43.

The first duct 33 preferably comprises a first pipe connecting the bifurcation 60 to the lower region 3a of the washing tub 3. The second duct 43 preferably comprises a second pipe, substantially having the same diameter of the first pipe but much longer than the first pipe, connecting the bifurcation 60 to the upper region 3b of the washing tub 3.

Preferably, in such a case, the recirculation lines 30, 40 are configured so that the liquid in the first recirculation line 30 requires a pressure P1 to fill the first volume V1 and then to reach the first region 3a of washing tub 3 which is lower than the pressure P2 required for the liquid to fill the second volume V2 in the second recirculation line 40 and to reach the second region 3b of the washing tub 3.

More preferably, in such a case, the ducts 33, 43 are configured so that the liquid in the first duct 33 requires a pressure P1 to fill the first volume V1 and then to reach the first region 3a of washing tub 3 which is lower than the pressure P2 required for the liquid to fill the second volume V2 in the second duct 43 and to reach the second region 3b of the washing tub 3.

In different embodiments, ducts of the recirculation system may be differently configured to achieve the same effect.

For example, the first and the second duct may have the same volume but extending at different highs.

According to a preferred embodiment of the invention, the recirculation pump 22 is a variable-speed pump, i.e. it can be driven in at least two different speeds.

In a preferred embodiment of the invention, the recirculation pump may be driven at two different fixed speeds S1, S2.

In a further preferred embodiment of the invention, the recirculation pump may be driven at more than two different fixed speeds S1, S2.

In a further preferred embodiment of the invention, the recirculation pump may be driven at variable speeds in a continuous way.

In case the recirculation pump 22 is a variable-speed pump, the first functioning condition is preferably obtained by driving the recirculation pump 22 at a first speed S1, as illustrated in FIG. 10A, and the second functioning condition is preferably obtained by driving the recirculation pump 22 at a second speed S2 higher than the first speed S1, as illustrated in FIG. 10B.

When the recirculation pump 22 is driven at the first functioning condition, i.e. at the first speed S1, a proper pressure is maintained at its outlet 26 so that the liquid in the first duct 33 reaches the first region 3a of washing tub 3 while the liquid in the second duct 43 does not reach the second region 3b of the washing tub 3.

When the recirculation pump 22 is driven at the second functioning condition, i.e. at the second speed S2, a proper pressure is maintained at its outlet 26 so that the liquid in the first duct 33 reaches the first region 3a of washing tub 3 and the liquid in the second duct 43 reaches the second region 3b of the washing tub 3.

According to a further preferred embodiment of the invention, the recirculation pump 22 is preferably a fixed speed pump. In this case, the first functioning condition of the recirculation pump 22 is preferably obtained by driving it so that its speed has a first pulsed waveform Sp1 having a first duty cycle D1, as illustrated in FIG. 11A. The first pulsed waveform Sp1 is preferably an on-and-off signal, wherein the recirculation pump 22 is opportunely switched on and off.

The first pulsed waveform Sp1 therefore preferably comprises a train of pulses.

The second functioning condition of the recirculation pump 22 is preferably obtained by driving it so that its speed has a second pulsed waveform Sp2 having a second duty cycle D2 higher than the first duty cycle D1, as illustrated in FIG. 11B. The second pulsed waveform Sp2 is also preferably an on-and-off signal, wherein the recirculation pump 22 is opportunely switched on and off.

The second pulsed waveform Sp2 therefore preferably comprises a train of pulses.

According to a further preferred embodiment of the invention, the recirculation pump 22 is preferably a variable speed pump and is driven so that its speed has a pulsed waveform. In this case, the first functioning condition of the recirculation pump 22 is preferably obtained by driving it so that its speed has a first pulsed waveform Sp1′. The first pulsed waveform Sp1′ preferably comprises a train of pulses different one to the other. The first pulsed waveform Sp1′ has a first average speed Sa1, as illustrated in FIG. 12A.

With the term “average speed” it has to be meant the average speed of the recirculation pump 22 in a predetermined time period within which the recirculation pump 22 comprises a plurality of pulses, i.e. is successively switched on and off.

Referring to FIG. 12A, the first average speed Sa1 is the average speed of the recirculation pump 22 in the predetermined time period Tp within which the recirculation pump 22 is successively switched on and off five times (a train of five pulses).

The second functioning condition of the recirculation pump 22 is preferably obtained by driving it so that its speed has a second pulsed waveform Sp2′. The second pulsed waveform Sp2′ preferably comprises a train of pulses different one to the other. The second pulsed waveform Sp2′ preferably has a second average speed Sa2 higher than the first average speed Sa1, as illustrated in FIG. 12B.

The second average speed Sa2 is the average speed of the recirculation pump 22 in said predetermined time period Tp.

Speed waveforms for the recirculation pump 2 shown and described above are some of the possible speed waveforms which may be preferably foreseen for the pump in the two functioning conditions described above.

According to an aspect of the invention, and according to the above description, it can be appreciated that the recirculation system 20 shows a threshold point between a condition wherein the liquid circulates only in the first recirculation line 30, or first duct 33, and a condition wherein the liquid circulates both in the first recirculation line 30 and the second recirculation line 40, or ducts 33, 43. Correspondingly, the recirculation pump 22 shows a working threshold wherein if the recirculation pump 22 works below the working threshold the liquid circulates only in the first recirculation line 30, or first duct 33, and if the recirculation pump 22 works above the working threshold the liquid circulates both in the first recirculation line 30 and the second recirculation line 40, or ducts 33, 43.

Preferably, therefore, according to the exemplary embodiments described above, in particular referring to FIGS. 10A-10B, 11A-11B and 12A-11B, it can be appreciated that:

- if the recirculation pump 22 is a variable-speed pump, the first functioning condition is obtained by driving the recirculation pump 22 at a first speed S1 below a threshold value Sth (see FIGS. 10A and 10B) and the second functioning condition is obtained by driving the recirculation pump 22 at a second speed S2 above the threshold value Sth;
- if the recirculation pump 22 is a fixed speed pump (see FIGS. 11A and 11B), the first functioning condition of the recirculation pump 22 is preferably obtained by driving it so that its speed has a first pulsed waveform Sp1 having a first duty cycle D1 below a threshold value Dth (not illustrated) and the second functioning condition of the recirculation pump 22 is preferably obtained by driving it so that its speed has a second pulsed waveform Sp2 having a second duty cycle D2 above a threshold value Dth;
- if the recirculation pump 22 is preferably a variable-speed pump and is drive with a pulsed signal, the first functioning condition of the recirculation pump 22 is preferably obtained by driving it so that its speed has a first pulsed waveform Sp1′ having a first average speed Sa1 below a threshold value Spth (see FIGS. 12A and 12B) and the second functioning condition of the recirculation pump 22 is preferably obtained by driving it so that its speed has a second pulsed waveform Sp2′ having a second average speed Sa2 above the threshold value Spth.

It can be appreciated that the two recirculation lines of the recirculation system according to the invention can be easily controlled by means of a single recirculation pump opportunely driven as described above. Advantageously, the liquid is selectively circulated through only the first duct 33 or through both the ducts 33, 43 and the bifurcation 60, while the recirculation system 20 does not require any valve as in the known system.

The laundry washing machine according to the invention has therefore a simplified structural construction with respect to the known laundry washing machines. Reliability is therefore increased and manufacturing and/or maintenance time and costs are reduced.

FIGS. 13 and 14 show a further preferred embodiment of the invention which differs from the preferred embodiment previously described in that the bifurcation 160 is T shaped, instead of Y shaped.

With reference to FIGS. 15 to 18, a recirculation system 220 according to a further preferred embodiment of the invention is described.

The recirculation system 220 preferably comprises a recirculation pump 222 having an inlet 24 connectable to the bottom 3a of the washing tub 3, preferably through a pipe 32 connected to the filtering device 12, and an outlet 226 for conveying liquid to the first and second recirculation lines 230, 240. Preferably, the outlet 226 is realized at a body portion 250 of the pump 222.

The first recirculation line 230 preferably comprises a first duct 233 and the second recirculation line 240 preferably comprises a second duct 243, similar to the first preferred embodiment previously described with reference to FIGS. 1 to 12.

Preferably, outlet 226 of the recirculation pump 222 conveys liquid to a bifurcation 260 for the first duct 233 and the second duct 243. Bifurcation 260, as better visible in FIG. 16, is realized also at the same body portion 250 of the pump 222. The bifurcation 260 is preferably substantially Y shaped and configured so that the two ducts 233, 243 substantially extend vertically from the bifurcation 260.

With reference to FIGS. 19 to 22, a recirculation system 320 according to a further preferred embodiment of the invention is described.

The recirculation system 320 preferably comprises a recirculation pump 322 having an inlet 24 connectable to the bottom 3a of the washing tub 3, preferably through a pipe 32 connected to the filtering device 12, and an outlet 326 for conveying liquid to the first and second recirculation lines 330, 340. Preferably, the outlet 326 is realized at a body portion 350 of the pump 322.

The first recirculation line 330 preferably comprises a first duct 333 and the second recirculation line 340 preferably comprises a second duct 343, similar to the first preferred embodiment previously described with reference to FIGS. 1 to 12.

Preferably, outlet 326 of the recirculation pump 322 conveys liquid to a bifurcation 360 for the first duct 333 and the second duct 343. Bifurcation 360, as better visible in FIG. 20, is realized also at the same body portion 350 of the pump 322. The bifurcation 360 is preferably substantially T shaped and configured so that the first duct 333 substantially extends horizontally from the bifurcation 360 and the second duct 343 substantially extends vertically from the bifurcation 360.

It has thus been shown that the present invention allows all the set objects to be achieved. In particular, it makes it possible to provide a laundry washing machine having a simplified structural construction with respect to the known laundry washing machines.

While the present invention has been described with reference to the particular embodiments shown in the figures, it should be noted that the present invention is not limited to the specific embodiments illustrated and described herein; on the contrary, further variants of the embodiments described herein fall within the scope of the present invention, which is defined in the claims.

LAUNDRY WASHING MACHINE AND METHOD FOR OPERATING THE LAUNDRY WASHING MACHINE

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